Processes of and machines for sintering ores



Jan. 3, 1967 H. FARBER 3,295,953

PROCESSES OF AND MACHINES FOR SINTERING ORES Filed Jan. 17, 1964 4 Sheets-Sheet 1 l/w z /vraP HANS FARBER WQ/MM ATTORNEY Jan. 3, 1967 H. FARBER 3,295,953

PROCESSES OF AND MACHlNES FOR SINTERING ORES Filed Jan. 17, 1964 4 Sheets-Sheet 2 INVENI'OIP lM/VS FARBE/P WQQUL ATTORNEY H. FARBER 3,

PROCESSES OF AND MACHINES FOR SINTERING ORES Jan. 3, 1967 4 Sheets-Sheet 3 Filed Jan. 17, 1964 K E M A mF m V5 M H ATTORNEY Jan. 3, 1967 H. FARBER 3,295,953

PROCESSES OF AND MACHINES FOR SINTERING ORES Filed Jan. 17, 1964 4 Sheets-Sheet 4 INVENTOR. H/mas FZ BL United States Patent Ofiice 3,295,953 Patented Jan. 3, 1967 Claims. (:L 75-5 This invention relates to improvements in processes of and machines for sintering or other heating of metallic ores.

Experience has taught that fine ore which is obtained by mining or by crushing relatively coarse orlump ore cannot be processed in a blast furnace without a special pretreatment. In such a pretreatment, the fine ore is sintered or heated to become suitable for being processed in the blast furnace.

Various processes and plants for treating fine ore are known, including so-called continuous plants, which comprise grate cars or pallets charged with the material to be treated (fine ore and coke and, if desired, additions). The pallets are arranged in succession on an endless track, which comprises an upper course and a lower course,

and are moved by a driving or lifting sprocket mechanism disposed at one end of the courses and arranged to engage the successive pallets sequentially. These pallets expand, of course, as the operating temperature rises .to its maximum value. The series of pallets must nevertheless be accommodated in the endless track without constraint, even when the series has become extended as a function of such thermal expansion.

To this end, it has been proposed heretofore to design the endless track so as to enable a variation of its length in adaptation to the thermal expansion. Alternatively, it has been proposed to design the endless track to have an invariable length which is so large that a heat expansion gap, corresponding to the maximum degree of thermal expansion to be expected, is formed between the leading and trailing ends of the continuous series of pallets. The

arrangement is such that this gap normally is formed at the discharge end of the upper course, i.e. at that arcuate portion of the endless track which leads from the upper course to the lower course and interconnects the same. Thus, the pallets fall through the gap in succession and without being braked. As a result, each of the respective falling pallets or cars, which just prior to the fall was the leading car of the series, comes up against the then last car of the series with a relatively violent shock or impact, particularly when the machine is being started up from a cold condition, which almost invariably causes damage both to the lfalling car and to the impacted car.

It is an important object of the present invention, therefore, to provide novel processes of and machines for sintering metallic ores which enable the expenditures involved in the variable-length endless track type of system and the disadvantages involved in the thermal expansion g-ap type of system to be advantageously avoided.

More specifically, it is an object of the present invention to provide means and arrangements facilitating the transfer of the individual pallets or cars between the courses of a fixed-length endless track without any impacting of any car or pallet against another while making use of a thermal expansion gap to accommodate the entire series of cars or pallets even in the most extended condition thereof.

Another object of the present invention is the provision of means and arrangements which in a thermal expansion gap type of fixed-length endless track permit a shock-tree transfer of the pallets both upwardly from the lower course and downwardly from the upper course.

In accordance with the general aspects of the present invention, the attainment of these objectives entails the elimination of both the falling movement of the pallets and the resulting shocks or impacts by a displacement of the gap, which is formed between the respective end pallets of the series and the size of which increases with the number of pallets, from the discharge end of the upper course to the vicinity of the drive sprocket means. More particularly, in implementing the principles of the invention, the heat or thermal expansion gap between the leading and trailing ends of said series of pallets or cars is maintained at the junction between the arcuatetransfer portion ofthe endless track adjacent the drive sprocket mean-s and the upper course of the endless track. Thus, for the movement of the pallets in one direction during the progress of a sintering operation, the gap is located at the discharge end of the said arcuate track portion along which the pallets are moved from the lower course to the upper course, with each pallet being lifted through said gap, while for the movement of the pallets in the reverse direction when no sintering operation is in progress, the gap is still at the same location which may be considered as the entrance end of the said arcuate track portion along which the cars are moved from the upper course to the lower course, with each pallet being lowered through the gap.

As will be more fully explained hereinafter, this has the result that the pallets remain in close succession not only in the upper and lower courses but also adjacent to the said arcuate track portion and, especially when being lifted through the gap by the drive sprocket means, are moved at the low peripheral velocity of the latter, approximately 0.05 meter per second.

The machine for sintering or other heating of metallic ores thus basically comprises means defining an endless track having an upper course, a lower course, a lifting arcuate track portion at one end of said courses, and a discharge arcuate track portion at the other end of said courses, a continuous series of ore-receiving pallets or cars which are adapted to be moved along said track, the leading and trailing ends of said series being spaced along said track in the cold condition of the machine by a heat expansion gap corresponding to the longitudinal thermal expansion of said series to be expected during the operation of said machine, said gap being disposed within said lifting arcuate tra'ck portion, and means .for lifting said pallets or cars individually and in succession through said gap and for driving each such pallet or car from said liftin-g arcuate track portion onto said upper course.

The foregoing and other objects, characteristics and advantages of the present invention will be more clearly understood afrom the following detailed description thereof when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic side elevational view of a sintering machine according to one embodiment of the present invention and shows the endless track with the pallets and the propelling sprocket means therefor;

FIG. 2 is a fragmentary illustration, on an enlarged scale, of the arcuate track portion along which the propelling sprocket means is in engagement with the pallets;

FIG. 3 is a diagrammatic side elevational view, similar to FIG. 1, of a modified form of the sintering machine according to this invention; and

FIG. 4 is a fragmentary top plan view of the machine at the arcuate feeding track end region thereof, and shows details of the sprocket means and drive mechanism therefor, certain parts being omitted for the sake of clarity.

Referring now to the drawings in greater detail, the

sintering machine S, shown only diagrammatically in FIG. 1 for the sake of simplicity, comprises an endless track T along which suitable receptacles, generally in the form of pallets or grate-bottomed cars 1, each having two sets of wheels 2, are guided in the usual manner. The track, which is constituted by a pair of horizontally spaced, parallel rail structures T and T" (FIG. 4) mounted on a suitably rigidified machine frame M, comprises an upper course 3, a lower course 4, an approximately semicircular, arcuate lowering portion 5 at one end (the discharge end), and an arcuate lifting portion 6 at the other end (the drive end) of the sintering machine. At this end is arranged a lifting sprocket device 7, the teeth of which are adapted to engage the axles of the pallets 1 in succession, as will be more fully explained presently.

The pallets pass through the endless track in the direction of the arrows 8, i.e. counterclockwise in FIG. 1, and at the initial portion of the upper course 3 are charged first from a hopper 9 with coarse pieces to form a base layer on the grates constituting the bottoms of the cars or pallets and then from a hopper 10 with the material to be sintered. The latter material consists of a mixture of fine ore and coke and, if desired, additions, such as lime. The base layer serves to prevent a fall of the fines from the hopper 10 through the respective grates and may be formed by coarse-grained ore or coarse-grained sinter. As is well known, the various pallets are openended structures and when in end to end relationship on the upper course 3 define a continuous trough, which enables the lowermost discharge end of the coarse hopper 9 to be generally located in close proximity to the plane of the grate car bottoms, i.e. at a level lower than that of the discharge end of the fine hopper 10 which is approximately at the level of the upper edges of the side walls of the cars. This permits the piling of the fines in the cars to the highest practical level and contributes to the maximum utilization of the respective capacities of the pallets or cars 1.

As seen in the direction of movement of the receptacles or palllets, an igniting tunnel 11 is disposed behind the hopper 10 in the usual manner. This tunnel contains gas or oil burners (not shown), which cause the mixed charge to be driedv and ignited as the pallets pass through the tunnel. The air required for combustion is sucked from above through the charge and the grates of the pallets. For this purpose, a plurality of wind boxes 12 are provided below the upper course 3 and are connected to a suction fan or the like. The sintered material falls out of the pallets 1 as they move along the discharge arcuate portion 5 of the track T and falls into a breaker, which is diagrammatically indicated at 13. The material discharged by this breaker is sized by screening. The residual fines are recharged to the mixture intended to fill the hopper 10.

Referring again to FIG. 4, the sprocket device 7 essentially comprises a pair of toothed wheels 7' and 7" secured, as by a flange connection, in precise alignment with each other to the opposite end faces of an intermediately drum D provided with circumferentially spaced rigiditying ribs D. The axle 14 of the drum D is rotatably journaled in a pair of bearings B and B, one end region of the axle 14 extending through the bearing B and being connected to a spur gear G of relatively large diameter which meshes with a driving pinion P of relatively smaller diameter mounted on the output shaft of a multi-stage transmission R. The input of the latter is connected via a coupling C to a hydraulic motor H to which oil or like hydraulic fluid is supplied in an infinitely variable quantity corresponding to the desired speed of rotation of the motor, whereby the operating speed of the motor can be infinitely varied in accordance with the required speed of movement of the pallets or cars 1 around the track T. Both the motor H and the transmission R are mounted in a supporting frame structure F one end region of which bears on an extension of the axle 14 and the other end region of which rests on a torque-opposing member M, e.g. a block or rigid post, constituting a part of the machine frame M. Concurrently, the bearings B and B are mounted, respectively, on a pair of slides B arranged for horizontal displacement radially of the axle 14 by means of a pair of adjusting spindles (not shown). By virtue of this bearing and support arrangement, it is possible to maintain a full driving engagement between the pinion P and the spur gear G even in the event of an inclination of the axle 14 in the horizontal plane, which inclination might become necessary if the cars in the upper course 3 of the track T were to asume oblique positions relative to their direction of movement under the influence of a differential thermal expansion thereof on the rail structures T and T.

To the extent so far described, the structure of the machine S is the same as that of a conventional sintering machine of the continuous or windbox type comprising a series of pallets or grate cars and an endless track of constant length. Just as in the known sintering machines of this type, the track T of the machine S is of such a length that a gap L for accommodating thermal expansion remains between the leading and trailing ends of the continuous series of pallets 1. The size of this gap will depend on the total length of the endless track and on the maximum temperature to be expected during the operation of the sintering machine. For instance, in a machine having a track length of about meters, the gap will be about mm. It has already been pointed out herein that in the known sintering machines this gap is always located at the discharge end of the track, i.e. at that end where the cars containing the sintered materials are transferred from the upper course to the lower course of the track, and reference has also been made to the disadvantages attending the resultant free-fall transfer of the cars through the gap.

In contradistinction thereto, in accordance with the principles of the invention the gap L is disposed adjacent to the lifting sprocket device 7, as is apparent from FIG. 1. This is due to the fact that the tooth pitch of the sprocket wheel device 7 is not equal to the pitch, i.e. the distance between the front axles of each two adjacent ones, of the series of pallets having an arcuate configuration along the arcuate lifting track portion 6, but exceeds this pitch of the pallets by the equalizing or thermal ex pansion gap L. This is illustrated particularly in FIG. 2.

The arrangement shown in FIG. 2 ensures a smooth drive of the pallets because the entry point of an arcuate lifting track section 6' connected to the upper course 3 at the drive end of the track T and extending, for example, along a quarter of a circle centered at 15, is located a distance a from the axis of rotation 14 of the sprocket device which is greater than the distance b from the said axis to the delivery point of said section 6'. The decrease of this distance in the direction of movement 8 of the pallets 1 has the result that the first pallet 1b (the then leading end of the series) engaged and driven by the parallel and aligned teeth 7b of the sprocket device 7 behind the gap L is guided by the arcuate section 6 progressively closer to the sprocket device 7 and thus progressively approaches the preceding pallet 1a (the then trailing end of the series) which is disposed beyond the gap and engaged an driven by the parallel and aligned teeth 7a of the sprocket device 7.

As is clearly discernible from FIG. 2, the teeth of the sprocket device 7 lift the pallets 1 in succession through the gap L without exerting a shock on the pallets. The rotation of the sprocket device 7 is controlled to impart to the pallets a speed which provides for the time required for the sintering operation to be carried out along the upper course 3. Thus, the circumferential speed of the sprocket device may be, for example, about 3 to 4 meters per minute. The sprocket device 7 is always in engagement with two pallets at a time, namely a pallet (1a in FIG. 2) preceding the gap L and a pallet (lb in FIG. 2) succeeding the gap L. To ensure that the pallets on the upper course 3 are moved continuously rather than intermittently, the section 6 (FIG. 2) of the lifting track portion 6 is not concentric with the sprocket device 7, but as pointed out above the distance between the arcuate feeding portion 6 and the axis 14 of the propelling sprocket device decreases from the value a to the value b in the direction of the upper course 3, i.e. in the direction 8 of the movement of the pallets.

Although in the embodiment shown, the section 6' is described as a quarter of a circle having a center 15, the same result could be achieved by a'spiral arcuate feeding section having a varying curvature along the length of the arc.

The engagement of the teeth of the sprocket device 7 with the successive pallets is effected as follows:

In the position shown in FIG. 2, each tooth 7a engages the pallet la and the following tooth 7b engages the pallet 1b, which trails the pallet 1a at a distance determined by the gap L. Through the intermediary of the pallet 1a, therefore, the teeth 7a impart a feeding motion to all the pallets 1 which are on the upper course 3. During the rotation of the sprocket device, the teeth 7a remain in engagement with the pallet 1a until the succeeding pallet lb has closed up to and come into contact with the pallet 1a, whereupon the pallet 1b then takes over without interruption the function of transmitting the pushing force of the sprocket device 7 (i.e. the teeth 7b thereof) to the pallets on the upper course ahead. FIG. 2 shows the position in which the engagement of each tooth 7b with the pallet 1b begins whereas the succeeding tooth 7c is not yet effective and does not engage the associated following pallet 1c.

A continued rotation of the sprocket device 7 from the position shown in FIG. 2 will cause a lifting of the pallet 1b from the succeeding pallet 10, and thus a decrease of the distance between the pallets 1a and 1b, due to the fact that the effective lever arm r from the sprocket axis 14 to the teeth 7b is larger than the lever arm r to the teeth 7a where the latter engage the pallet 1a. All teeth having the same angular velocity, the velocity of the pallet 1b will necessarily be larger than that of the pallet 1a. The consequent relative movement between pallets 1a and 1b ensures, therefore, that the gap L between them is progressively closed and is re-forrned towards the rear, between the pallets 1b and 10.

While the gap L between 1a and 1b is being closed, the pallet is not being driven by the teeth 71: but nevertheless is lifted along the track portion 6 by the action of the weight of the pallets passing through the arcuate discharging or lowering portion 5 at the speed imparted by the teeth 7a to the pallets on the upper course 3. The pallet 1c will lag behind the pallet 1b in accordance with the relative movement between the pallets 1a and 1b. When the pallet 10 has'been thus pushed ahead and the sprocket device 7 has been rotated through one tooth pitch, the teeth 7c take over the driving function. The cycle which has been described hereinbefore begins again after all pallets have been advanced by one pallet length from the position of FIG. 2.

The position shown in FIG. 2, in which one pair of teeth engages the pallet which immediately succeeds the gap L, is so chosen that the combined action of the weight of the pallets guided along the arcuate lifting portion 6 and of the traveling resistance of the pallets along the lower course 4 will maintain the pallets in a close succession also along the arcuate discharging portion 5, so that the gap cannot be formed in this region. The possibility of an unbraked or free fall of the pallets at the discharging portion 5 is, therefore, effectively eliminated.

It will be understood that the tooth 7b in FIG. 2 will not yet have engaged the pallet 1b when an increased thermal expansion has resulted in a decrease of the gap L so that the pallet 1b is still spaced ahead of the said tooth 7b.

Experience has shown that a replacement of individual pallets and other repair work is facilitated when the sprocket device 7 is used to drive the pallets in a direction 8' (FIG. 3) opposite to the direction 8. In such a case, however, the effective lever arms of the teeth 7a and 7b (FIG. 2) increase from r to 1' The may cause a jamming of the pallets between the teeth and the track in the region in which a disengagement of the teeth is necessary.

To the end of avoiding this potential drawback, in accordance with the aspect of the present invention illustrated in FIG. 3, the lower section 6 of the arcuate track portion 6 is also designed as an arcuate feeding section for a movement of the pallets in the direction 8. The lower arcuate feeding section 6" has mirror symmetry with respect to the upper section 6 and connects the latter to the lower course 4 of the track. It will be apparent, therefore, that when the pallets 1 are driven in the direction 8', the section 6" guides them progressively closer to the sprocket device 7 in such a manner as to reduce the eifective lever arms of the teeth in the same manner in which the pallets were guided by the upper section 6 during their movement in the direction 8.

In operation, when the sprocket device 7 is rotated from the position shown in FIG. 3 in the direction of the arrow 8', all pallets will initially remain at rest until the teeth 72 engages the pallet 1e. All the pallets on the lower course 4, on the arcuate track portion 5 and on the upper course 3 will then be pushed together with the pallet 16. The teeth 7a, 7b, 7c and 7d are not effective in this pushing movement. Before the teeth 7e become disengaged from the pallet Ie, the teeth 7d take over the rearward movement of the pallets and so forth.

It will be understood that the foregoing description of preferred aspects of the sintering processes and machines according to the present invention is for the purpose of illustration only, and that the disclosed structures and structural arrangements are subject to a number of changes and variations none of which involves any departure from the spirit and scope of the present invention as defined in the hereto appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. The process of moving a continuous series of end to end abutting pallets of a sintering machine along an endless track having an upper course, a lower course and arcuate track portions interconnecting said upper and lower courses at the opposite ends thereof, the total length. of said continuous series of pallets in the cold condition of the machine being less than that of said track by a heat expansion gap corresponding in size to the longitudinal thermal expansion of said continuous series of pallets to be expected during the operation of the machine; comprising the steps of maintaining said heat expansion gap between the leading and trailing ends of said continuous series of pallets in the region of one of said arcuate track portions, providing drive means adjacent said one arcuate tr-ack portion for engagement at any given time only with the then leading and trailing ones of said continuous series of pallets of which said leading pallet is at that time to 'be transferred through said heat expansion gap into engagement with said trailing pallet, and actuating said drive means to advance said trailing pallet and therethrough all the remaining interengaged pallets of said series and simultaneously to displace said leading pallet through said heat expansion gap at a speed initially in excess of but decreasing to the speed of movement of said trailing pallet, whereby said leading pallet is brought in a substantially shock-free manner into contact with said trailing pallet of said series.

2. A sintering process, comprising the steps of providing a continuous series of end to end abutting pallets arranged for movement in the longitudinal direction of said series along an endless track having an upper course, a lower course and arcuate track portions interconnecting said upper and lower courses at the opposite ends thereof, treating the materials in said pallets at elevated temperatures along a predetermined portion of said upper course, the total length of said continuous series of pallets in cold condition being less than that of said track by a heat expansion gap corresponding in size to the longitudinal thermal expansion of said continuous series of pallets to be expected during the sintering operation, maintaining said heat expansion gap between the leading and trailing ends of said continuous series of pallets in the region of one of said arcuate track portions, providing drive means adjacent said one arcuate track portion for engagement at any given time only with the then leading and trailing ones of said continuous series of pallets of which said leading pallet is at that time to be transferred through said heat expansion gap into engagement with said trailing pallet, and actuating said drive means to advance said trailing pallet and therethrough all the remaining interengaged pallets of said series and simultaneously to displace said leading pallet through said heat expansion gap at a speed initially in excess of but decreasing to the speed of movement of said trailing pallet, whereby said leading pallet is brought in a substantially shock-free manner into contact with said trailing receptacle of said. series.

3. A sintering machine, comprising an endless track having an upper course, a lower course, a lifting arcuate track portion at one end of said courses, and a lowering arcuate track portion at the other end of said courses, a continuous series of end to end engaging pallets in said track which are adapted to receive the material being sintered and to be moved along said track, the total length of said continuous series of pallets in the cold condition of the machine being less than the length of said endless track by a heat expansion gap corresponding in size to the longitudinal thermal expansion of said continuous series of pallets to be expected during the operation of the machine, said gap being disposed in the region of said lifting arcuate track portion, and drive means operable to engage at any given time only the then leading and trailing pallets of said continuous series for advancing said trailing pallet and therethrough all the re maining interenga-ged pallets of said series and for simultaneously lifting said leading pallet through said heat expansion gap away from the remainder of said continuous series and toward said trailing pallet at a speed initially in excess of but decreasing to the speed of movement of said trailing pallet, whereby said leading pallet is brought into shock-free contact with said trailing pallet of said series.

4. A machine according to claim 3, said heat expansion gap being disposed adjacent the junction between said lifting arcuate track portion and said upper course.

5. A machine according to claim 3, said drive means comprising a sprocket wheel device rotatably mounted 8 adjacent said lifting arcuate track portion, said pallets having respective identically positioned elements engageable by the teeth of said sprocket wheel device, and the pitch of said teeth of said sprocket wheel device exceeding the distance between said elements of each successive pair of pallets by at least said heat expansion gap.

6. A machine according to claim 5, said lifting arcuate track portion comprising an upper section which adjoins and merges with said upper course at an upper delivery point, said upper section further having a lower receiving point which is spaced from said upper delivery point by an angle of approximately thelinear distance between the axis of rotation of said sprocket wheel device and said upper section of said lifting arcuate track portion being a maximum at said receiving point and decreasing gradually to a minimum at said delivery point in a manner predetermined in accordance with the degree to which the pitch of said teeth of said sprocket wheel device exceeds the distance between said elements of each successive pair of pallets, said heat expansion gap being disposed between said receiving and delivery points, whereby each leading pallet of said series is, upon being engaged and lifted by said sprocket wheel device, guided closer to the latter by said upper section of said lifting arcuate track portion while concurrently being caused to progressively approach the then trailing pallet.

7. A machine according to claim 6 said lifting arcuate track portion further comprising a lower section which connects said lower course with said receiving point of said upper section and which has mirror symmetry with respect to said upper section.

8. A machine according to claim 6, said upper section of said lifting arcuate track portion having the curvature of an arc of a circle the center of which is spaced from said axis of rotation of said sprocket wheel device in accordance with the desired diiferen-ce between the respective distances of said receiving and delivery points of said upper section from said axis.

9. A machine according to claim 8, said lifting arcuate track portion further comprising a lower section which connects said lower course with said receiving point of said upper section and which has mirror symmetry with respect to said upper section,

10. A machine according to claim 3, said heat expansion gap in the cold condition of the machine exceeding the maximum expected longitudinal thermal expansion of said continuous series of pallets.

References Cited by the Examiner UNITED STATES PATENTS BENJAMIN HENKIN, Primary Examiner. 

1. THE PROCESS OF MOVING A CONTINUOUS SERIES OF END TO END ABUTTING PALLETS OF A SINTERING MACHINE ALONG AN ENDLESS TRACK HAVING AN UPPER COURSE, A LOWER COURSE AND ARCUATE TRACK PORTIONS INTERCONNECTING SAID UPPER AND LOWER COURSES AT THE OPPOSITE ENDS THEREOF, THE TOTAL LENGTH OF SAID CONTINUOUS SERIES OF PALLETS IN THE COLD CONDITION OF THE MACHINE BEING LESS THAN THAT OF SAID TRACK BY A HEAT EXPANSION GAP CORRESPONDING IN SIZE TO THE LONGITUDINAL THERMAL EXPANSION OF SAID CONTINUOUS SERIES OF PALLETS TO BE EXPECTED DURING THE OPERATION OF THE MACHINE; COMPRISING THE STEPS OF MAINTAINING SAID HEAT EXPANSION GAP BETWEEN THE LEADING AND TRAILING ENDS OF SAID CONTINUOUS SERIES OF PALLETS IN THE REGION OF ONE OF SAID ARCUATE TRACK PORTION FOR ENGAGEMENT AT ANY GIVEN TIME ONLY WITH THE THEN LEADING AND TRAILING ONES OF SAID CONTINUOUS SERIES OF PALLETS OF WHICH SAID LEADING PALLET IS AT THAT TIME TO BE TRANSFERRED THROUGH SAID HEAT EXPANSION GAP INTO ENGAGEMENT WITH SAID TRAILING PALLET, AND ACTUATING SAID DRIVE MEANS TO ADVANCE SAID TRAILING PALLET AND THERETHROUGH ALL THE REMAINING INTERENGAGED PALLETS OF SAID SERIES AND SIMULTANEOUSLY TO DISPLACE SAID LEADING PALLET THROUGH SAID HEAT EXPANSION GAP AT A SPEED INITIALLY IN EXCESS OF BUT DECREASING TO THE SPEED OF MOVEMENT OF SAID TRAILING PALLET, WHEREBY SAID LEADING PALLET IS BROUGHT IN A SUBSTANTIALLY SHOCK-FREE MANNER INTO CONTACT WITH SAID TRAILING PALLET OF SAID SERIES.
 3. A SINTERING MACHINE, COMPRISING AN ENDLESS TRACK HAVING AN UPPER COURSE, A LOWER COURSE, A LIFTING ARCUATE TRACK PORTION AT ONE END OF SAID COURSES, AND A LOWERING ARCUATE TRACK PORTION AT THE OTHER END OF SAID COURSES, A CONTINUOUS SERIES OF END TO END ENGAGING PALLETS IN SAID TRACK WHICH ARE ADAPTED TO RECEIVE THE MATERIAL BEING SINTERED AND TO BE MOVED ALONG SAID TRACK, THE TOTAL LENGTH OF SAID CONTINUOUS SERIES OF PALLETS IN THE COLD CONDITION OF THE MACHINE BEING LESS THAN THE LENGTH OF SAID ENDLESS TRACK BY A HEAT EXPANSION GAP CORRESPONDING IN SIZE TO THE LONGITUDINAL THERMAL EXPANSION OF SAID CONTINUOUS SERIES OF PALLETS TO BE EXPECTED DURING THE OPERATION OF THE MACHINE, SAID GAP BEING DISPOSED IN THE REGION OF SAID LIFTING ARCUATE TRACK PORTION, AND DRIVE MEANS OPERABLE TO ENGAGE AT ANY GIVEN TIME ONLY THE THEN LEADING AND TRAILING PALLETS OF SAID CONTINUOUS SERIES FOR ADVANCING SAID TRAILING PALLET AND THERETHROUGH ALL THE REMAINING INTERENGAGED PALLETS OF SAID SERIES AND FOR SIMULTANEOUSLY LIFTING SAID LEADING PALLET THROUGH SAID HEAT EXPANSION GAP AWAY FROM THE REMAINDER OF SAID CONTINUOUS SERIES AND TOWARD SAID TRAILING PALLET AT A SPEED INITIALLY IN EXCESS OF BUT DECREASING TO THE SPEED OF MOVEMENT OF SAID TRAILING PALLET, WHEREBY SAID LEADING PALLET IS BROUGHT INTO SHOCK-FREE CONTACT WITH SAID TRAILING PALLET OF SAID SERIES. 